The invention is based on a fuel injection device for internal combustion engines and on a method for fuel injection. In such fuel injection devices, the injection quantity is controlled either by control edges between the pump piston and the cylinder or by a magnet valve. In controls via a magnet valve, two basic systems are known for embodying the high-pressure circuit in high-pressure-controlled unit fuel injectors.
In one system, filling of the pump work chamber takes place directly via a magnet valve. This has the advantage that the electrically controlled unit fuel injector is intrinsically safe even if the magnet valve fails, and even if that valve should remain in the closed state, because no fuel is injected since filling of the pump work chamber with fuel is no longer taking place.
In the other system, filling of the pump work chamber takes place via the injection nozzle and the magnet valve. This system offers the advantages of improved cooling of the nozzle and better stability of the nozzle opening and closing process, but on the other hand has the disadvantage of relatively long line paths between the magnet valve and the pump work chamber, which if they are overly long worsen the injection performance, since the pressure losses in this line become so relatively great that filling via the magnet valve can no longer be assured under all operating conditions. Moreover, in this design, to assure the rapid filling of the pump work chamber, this filling is also done via a separate filling bore, so the intrinsic safety attained in the first system is lost as well.